Initializing your variables to proper value is must because it pays you better to initialize your variables properly while declaring them. If you don't initialize the variables then either they will cause compiler error or will be initialized with default values.
Getting a compiler error for uninitialized variable is better because it will result in making you properly initialize your variable but if you are careless then you may initialize your variables to null to avoid the compiler error.
The variables which will result in compiler error are method local and final variables.
The problem with null initialized variables is that they will cause NullPointerException if you forget to initialize them even by the time you try to access them. The biggest issue here is that the JVM does not point out the variable which is Null. You need to debug your Java application to be able to find the variable which caused NullPointerException.
Thus it is always advisable to properly initialize all the variables at all levels. If you don't have any value to be assigned to a variable at compile time and will assign an object/value at run time then it is better to initialize them to empty values.
Default initialization is fine with respect to primitive variable but the reference variables are again initialized to NULL values.
The issue with Null initialization becomes clear from the below code:
The above code will result in NullPointerException and if the line 6 is executed after some 1000 lines of logic and the user only reports that there is a NullPointerException thrown by the application then it may take you some 4-5 hours to find out which variable was not being initialized properly.
The reason for this failed initialization may be unavailability of properties file in some particular folder or connection problems.
However consider the following code:
The above code will not cause NullPointerException because of empty initialization and if the variable aList is not properly initialized at run time then the user may report there is no UI component seen on the screen or no file names are populated in the Text area. The user in this case will report a functionality issue which gives better idea of the problem from user as well as developer point.
Thus it all points out to the fact that always properly initialize your variables or initialize them to empty values if they will be assigned values at run time.
Getting a compiler error for uninitialized variable is better because it will result in making you properly initialize your variable but if you are careless then you may initialize your variables to null to avoid the compiler error.
The variables which will result in compiler error are method local and final variables.
The problem with null initialized variables is that they will cause NullPointerException if you forget to initialize them even by the time you try to access them. The biggest issue here is that the JVM does not point out the variable which is Null. You need to debug your Java application to be able to find the variable which caused NullPointerException.
Thus it is always advisable to properly initialize all the variables at all levels. If you don't have any value to be assigned to a variable at compile time and will assign an object/value at run time then it is better to initialize them to empty values.
Default initialization is fine with respect to primitive variable but the reference variables are again initialized to NULL values.
The issue with Null initialization becomes clear from the below code:
1 2 3 4 5 6 7 8 9 10 11 12 | package example.java;import java.util.ArrayList;public class Foo{ static ArrayList aList3 = null; public static void main(String[] args) { System.out.println(aList2.size()); // line 6 }} |
The above code will result in NullPointerException and if the line 6 is executed after some 1000 lines of logic and the user only reports that there is a NullPointerException thrown by the application then it may take you some 4-5 hours to find out which variable was not being initialized properly.
The reason for this failed initialization may be unavailability of properties file in some particular folder or connection problems.
However consider the following code:
1 2 3 4 5 6 7 8 9 10 11 12 | package example.java;import java.util.ArrayList;public class Foo{ static ArrayList aList3 = new ArrayList(); public static void main(String[] args) { System.out.println(aList3.size()); }} |
The above code will not cause NullPointerException because of empty initialization and if the variable aList is not properly initialized at run time then the user may report there is no UI component seen on the screen or no file names are populated in the Text area. The user in this case will report a functionality issue which gives better idea of the problem from user as well as developer point.
Thus it all points out to the fact that always properly initialize your variables or initialize them to empty values if they will be assigned values at run time.
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